Breaking Russia economically and causing a regime change was the hare brained scheme from the west. However, that whole plan relied on being able to sanction Russia effectively. The reality is that Russia is just too big and too integrated into the global economy for that to happen. So, when the west started trying to freeze Russia out of the global financial system they found out that India and China weren't on board, at which point the whole scheme fell apart.

What's worse, we're now seeing that it's actually the west that's having growing economic troubles while Russian economy is growing and domestic industry is developing. The relative cost of keeping this war going is far more significant for the west than for Russia. Europe in particular is screwed because they got cut off from cheap energy they were getting. Meanwhile, Russia has no problem selling energy to other countries. So, in practice it's Russia breaking NATO through attrition as opposed to the other way around.

The west trying to go the terrorist route is a possible scenario, and it has been openly discussed. However, that carries dangers of its own as well. What's likely to happen is that Russia will annex all the regions that are heavily populated by the Russian speaking population. People there just want the war to end, and they will integrate into Russia. Then there's going to be a rump state of western Ukraine left that's full of nationalists. It's not going to be able to function on its own, and it will become west's problem because if it fails then there will be a flood of refugees coming to Europe. This is the nightmare scenario for the west where they either have to keep pumping billions of dollars to prop up whatever's left of Ukraine or deal with a huge flood of refugees that Europe's not able to absorb.

And of course, the fascists will end up feeling betrayed by the west at this point and they will realize they've been cynically used. I expect there will be at least as much terrorism happening in Europe as in Russian controlled territory as a result. CBS put out a report a while back stating that only 30% of the weapons made it to the battlefront. The rest end up on the black market, and it's almost certain that Ukrainian fascists have been linking up with far right cells across Europe and feeding these weapons to them.

So, I agree with you that this is the likely US plan, but I predict that it's going to backfire the same way the proxy war did. US completely misread the situation and they've made huge blunders over the past two years that are now culminating in a debacle for them.